Conventional electron beam detectors, when measuring an electron beam of strong intensity, perform detection of the electron beam by measuring the current value produced by the electron beam, but, in the case of measurement of an electron beam of comparatively low intensity, the amount of charge produced by the electron beam is small, so it is not possible to detect the electron beam efficiently. Accordingly, in the case of an electron beam detector used in for example a scanning electron microscope (SEM), measurement is conducted by irradiating a sample surface with the electron beam, collecting the secondary electrons generated at this sample surface and using these to irradiate a phosphor, and detecting the fluorescence generated by this phosphor using a photomultiplier tube (photodetector). As such phosphors, the various types of phosphor shown in FIG. 9 are known; this table shows the phosphor, response speed, light emission intensity, life performance, light emission wavelength, and material (photoelectric surface) of the fluorescence detector. The order of excellence in this table is indicated by the symbols: double circle, circle, triangle, and cross.
In recent years, in the field of scanning electron microscopes or mass spectroscopes, phosphors are being demanded that provide high light emission intensity and fast response speed. The reason for this is that for example in the case of a scanning electron microscope, if the speed of response of the phosphor is fast, the scanning speed can consequently be made fast, making it possible to improve the performance of the equipment.                Patent reference 1: International Laid-open Patent Application No. 02/061458 pamphlet        
However, in the case of a conventional phosphor as shown in FIG. 9, there was the problem that it was difficult to obtain a fast response speed (of the order of μsec) sufficient for a scanning electron microscope or mass spectroscope. It should be noted that, of the small number of phosphors with which a good response speed is obtained, GaAsP light-emitting bodies have a low intensity of light emission and so were unsuitable for application to scanning electron microscopes and the like.